1. Field of the Invention
The present invention relates to an apparatus and method for stacking layers of items. More specifically, an apparatus and method for stacking superimposed layers of items, such as elongated items, either with or without the use of separation material between one or more of the superimposed layers.
2. Discussion of the Background
In the lumber industry, logs are initially cut into boards having various predetermined dimensions. Freshly cut boards are then generally sorted by width and length. Typically, the sorted boards are then arranged in stacks for storage, shipping, or further processing.
Dry boards are less likely to warp or subsequently change shape, thereby increasing their value. Therefore, freshly cut boards may be stacked for drying in a dry atmosphere, such as a dry kiln. In order to dry the boards in an efficient manner (quickly and in a substantially uniform manner along the length thereof), the boards may be stacked in layers with open spaces provided between each layer to enable drying gases to circulate through the stack. Therefore, during the stacking process, elongated wooden slats called “stickers” may be placed transversely between the layers of boards at spaced intervals along the length of the stack in order to separate the layers. Usually, the stickers have lengths equal to the width of the stack and are positioned transverse to the boards in the stack. The stickers are placed at desired intervals along the length of the stack to separate the layers of the boards to enable drying gases to circulate through the stack to uniformly and more quickly dry the boards.
Once the lumber boards are dry, the boards are typically taken to be dressed or planed to exact dimensions, and then the boards are trimmed to length. These finished boards are then typically stacked in a manner that is referred to as “dead packed,” which means there are not stickers provided between each layer. In such dead packed stacks, typically a wooden strip called a “lath” is provided between a predetermined number of layers to prevent an out of square effect of the stack. For example, ten layers are placed directly on top of each other without anything between the layers, and then a lath is placed transversely across the boards at the top of the stack at predetermined intervals along the length of the stack, and then ten more layers are placed directly on top of each other without anything between the layers, which results in a complete “dead packed” package.
Related art stacking devices typically use a device to receive a first layer of boards, transfer the first layer in a horizontal direction, and discharge the first layer at a stacking position. The device will then move horizontally to return to the starting position in order to lift a second layer of boards to transfer and discharge the second layer in the same manner as the first layer. The inventor of the present invention has determined that such a device is inefficient in that it only has the ability to transfer and stack one layer at a time. Additionally, such a configuration is inflexible in that device does not allow for any variation in height between the position at which the layer is received and discharged. Furthermore, such a device does not incorporate a device for inserting stickers or a lath between layers.